This type of a navigation apparatus is mounted to the side of a driver's seat, and carries out driving assistance by displaying a recommended route from a starting point to a destination point on, for example, on a liquid crystal display, and providing an appropriate route (recommended route) to the destination point to the driver.
Presently, this type of search for a recommended route is carried out by combining information about traffic congestion, traffic regulations, construction, traffic accidents and the like, that has been collected at a traffic information center, and the information about the time that is necessary to pass through a “link” that is set at a distance of hundreds of meters to several kilometers on major arterial roads.
Executing what is determining route deviation identification has been proposed for the navigation state in which this type of recommended route is found.
A navigation apparatus that has this configuration is provided with a route deviation identifying portion that identifies whether or not the position of the guided vehicle has deviated from the recommended route. In the case in which the route deviation identifying portion has identified that the position of the guided vehicle has deviated from the recommended route, from the point in time that this identification is made (the position of the guided vehicle at the time of this identification), the recommended route searching portion is activated to search for a new recommended route to the destination point.
Therefore, when the guided vehicle has deviated from a route, the user is provided with a recommended route that is found by the navigation apparatus by carrying out a new search, and the user can arrive at the destination point after deviating from a route.
Problems that occur with this type of route deviation plan in this situation will be explained with reference to FIG. 12A and FIG. 12B.
FIG. 12 shows a situation in which this type of route deviation has occurred, and the vehicle is traveling on a one-way road that has a plurality of lanes. In FIG. 12, the roads are all one-way roads, and the horizontal cruising road that runs in the left to right direction in the figure depicts a left horizontal cruising road ra that has four lanes, and vertical cruising roads that run from top to bottom in the figure depict three-lane vertical cruising roads. Furthermore, the left vertical cruising road rbl that is on the left side of the figure and the right vertical cruising road rbr that is on the right side are examples of roads that run in the vertical direction.
For a road network that has the structure described above, the recommended route Ro, which has been searched for and provided by the recommended route searching portion, is set from a starting point S side in the lower left of the figure to a destination point D side that is ahead on the right vertical cruising road rbr.
In such a traffic network, the guided vehicle successively receives navigation instructions from the navigation apparatus. In a road network having such a configuration, when attempting to enter from the lower left point of the left vertical cruising road rbl in the figure, it is necessary to use the upper cruising lane as far as possible, in order to enter the right vertical cruising road rbr at the horizontal cruising road portion (this position is referred to as the intermediate road position rm), which is between the left vertical cruising road rbl and the right vertical cruising road rbr.
However, as shown in FIG. 2B, at this intermediate road position, there are cases in which, due to some sort of condition, it is possible to enter only at the cruising lane on the lowest side. This type of problem may be, for example, a case in which the intermediate road position rm is congested and the guided vehicle cannot select an appropriate lane, or a case in which the user is not aware that there is a lane selection to be made and has simply entered the lowest lane.
Even in this situation, because at this moment the vehicle has entered the intermediate road position rm, the navigation apparatus does not identify that the guided vehicle has deviated from the route at the intermediate road position rm.
In the intermediate road position rm, in the case in which a mistaken lane selection has been made and the vehicle can only travel straight along the horizontal travel road ra, the vehicle proceeds forward and then actually deviates from the route.
This situation is recognized by the navigation apparatus, and at this stage (the state in which the point C in FIG. 12A has been passed), the route deviation plan portion first operates, the present position B is set to the starting point, as shown in FIG. 12B, and the route search to the destination point is carried out. As a result, a blank interval shown by the time lag between the points C and B occurs in the navigation according to a newly found recommended route, which is not preferable.
As an example of a technology for suppressing the occurrence of such blank intervals, a technology has been proposed in which a deviation from the recommended route is anticipated, and recommended routes to be used after this deviation are found in advance (Patent Document 1).
Furthermore, technology exists in which a backup route is found in advance only for recommended intersection points with the object of reducing the amount of calculation in Patent Document 1 (Patent Document 2).
Patent Document 1: Japanese Patent Application Publication No. JP-A-HEI8-30193 (claims)
Patent Document 2: Japanese Patent Application Publication No. JP-A-2003-344077 (claims)